U.S. patent application number 11/990948 was filed with the patent office on 2009-12-03 for uv protective coatings.
This patent application is currently assigned to International Technology Center. Invention is credited to Varvara P. Grichko, Olga Alexander Shenderova.
Application Number | 20090297828 11/990948 |
Document ID | / |
Family ID | 37809190 |
Filed Date | 2009-12-03 |
United States Patent
Application |
20090297828 |
Kind Code |
A1 |
Shenderova; Olga Alexander ;
et al. |
December 3, 2009 |
Uv protective coatings
Abstract
A surface coating, colorant, pigment or polymer composite
preparation that provides resistance to degradation when exposed to
at least some portion of ultraviolet radiation having wavelengths
between approximately 190 and 400 nm is made up of a dispersion of
an effective amount of diamond nanoparticles in a binding matrix,
wherein at least a portion of the diamond nanoparticles have a size
greater than about 60 nm so that the diamond particles provide
ultraviolet radiation degradation resistance properties in the
dispersion. This abstract is not to be considered limiting, since
other embodiments may deviate from the features described in this
abstract.
Inventors: |
Shenderova; Olga Alexander;
(Raleigh, NC) ; Grichko; Varvara P.; (Raleigh,
NC) |
Correspondence
Address: |
RADER FISHMAN & GRAUER PLLC
LION BUILDING, 1233 20TH STREET N.W., SUITE 501
WASHINGTON
DC
20036
US
|
Assignee: |
International Technology
Center
Raleigh
NC
|
Family ID: |
37809190 |
Appl. No.: |
11/990948 |
Filed: |
August 25, 2006 |
PCT Filed: |
August 25, 2006 |
PCT NO: |
PCT/US2006/033626 |
371 Date: |
August 7, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60712507 |
Aug 30, 2005 |
|
|
|
Current U.S.
Class: |
428/323 ;
106/472; 524/496 |
Current CPC
Class: |
C09D 5/32 20130101; A61K
8/30 20130101; C08K 3/04 20130101; A61K 8/0241 20130101; C04B
2111/00482 20130101; Y10T 428/25 20150115; A61K 8/19 20130101; A61K
2800/413 20130101; A61K 2800/614 20130101; A61Q 17/04 20130101;
A61K 2800/412 20130101; C09D 7/61 20180101; C09D 7/68 20180101;
C04B 2111/2076 20130101; C09D 7/67 20180101; A61K 8/04 20130101;
C04B 26/02 20130101; A61K 2800/81 20130101; A61K 2800/43 20130101;
C09K 11/65 20130101; C04B 26/02 20130101; C04B 14/022 20130101;
C04B 20/008 20130101; C04B 2103/54 20130101 |
Class at
Publication: |
428/323 ;
524/496; 106/472 |
International
Class: |
B32B 5/16 20060101
B32B005/16; C08K 3/04 20060101 C08K003/04; C09C 1/44 20060101
C09C001/44 |
Claims
1. A surface coating or colorant preparation that provides
resistance to degradation when exposed to at least some portion of
ultraviolet radiation having wavelengths between approximately 190
and 400 nm comprising: a dispersion of an effective amount of
diamond nanoparticles in a binding matrix, wherein at least a
portion of the diamond nanoparticles have a size greater than about
60 nm so that the diamond particles provide ultraviolet radiation
degradation resistance properties in the dispersion.
2. The surface coating or colorant according to claim 1, further
comprising a pigment that renders coloration to the surface coating
or colorant.
3. The surface coating according to claim 1, further comprising a
solvent that is compatible with the binder.
4. The surface coating or colorant preparation according to claim
1, wherein at least a portion of the diamond nanoparticles have a
size of approximately 60-150 nm.
5. The surface coating or colorant preparation according to claim
1, wherein at least a portion of the diamond nanoparticles have a
size of approximately 100 nm.
6. The surface coating or colorant preparation according to claim
1, wherein the diamond nanoparticles comprise up to 25.0 percent by
weight of the surface coating or colorant.
7. The surface coating or colorant preparation according to claim
1, wherein the diamond nanoparticles comprise between about 0.5 and
5.0 percent by weight of the preparation.
8. The surface coating or colorant of claim 1, wherein the
nanodiamond particles have a visible color or are luminescent, and
wherein the diamond nanoparticles impart a color to or modify a
color of the dispersion.
9. The surface coating or colorant according to claim 1, formulated
as a paint, varnish, lacquer, enamel, polycarbonate and
polycarbonate blends, polyester, polyester fibers, polybutylene
terephthalate (PBT), acrylics, polyamide, polyamide fibers,
polyacetal, polyesters, unsaturated polyesters, polyurethane,
styrenics and other plastics and coatings.
10. The surface coating or colorant according to claim 1, wherein
the diamond nanoparticles are modified as a result of wet or gas
phase chemical reaction(s), or chemical reactions induced
photochemically, electrochemically, mechanochemically, annealing,
or by means of a plasma, irradiation or sonic energy to obtain
diamond nanoparticles with an enhanced ability to absorb
ultraviolet radiation.
11. The UV radiation attenuating material in accordance with claim
1, wherein the binding matrix is selected from the group consisting
of: a polymer matrix, an epoxy, polytetrafluoroethelyne, resins,
polycarbonates and polycarbonate blends, polystyrene,
polyurethanes, polyimides, acrylics, epoxies, methacrylic,
phenolics, silicones, polyesters, polyester fibers, unsaturated
polyesters, polyurethane foam (PUF), polybutylene terephthalate
(PBT), polyamides, polyamide fibers, polyacetals, vinyl polymers,
phenol formaldehyde, neoprene, rubber, silicone rubber compounds,
polypyrroles, polyaniline, polyacetylenes, polythiophenes,
poly-p-phenylenes, polyacrylthiophenes,
poly-p-phenylene-benzo-biz-thiozole (PBT), polymethylmethacrylate,
butadieneacrylonitrile, fibers, ceramics, glasses, polyethyelene
compounds with polyisobutylene, ethylene ethyl acrylate copolymers,
extruded polystyrene foam, and expanded polyvinylchloride and other
plastics and coatings.
12. The UV radiation attenuating material in accordance with claim
1, wherein the binding matrix containing the UV radiation
attenuating nanodiamond particles is suitable for application as a
coating to a substrate using at least one of an aerosol spray
process, an electrostatic spray process, a hot melt spray process,
a high velocity high temperature spray process, a thermal spray
process, an ultrasonic spray process, a fluidized bed process, a
dipping process, a brushing process, a spin-on process, a wipe-on
process, a plasma spraying process, a casting process, a molding
process and an injection molding process.
13. An article coated by the surface coating or colorant of claim
1.
14. A paint or surface coating preparation that provides resistance
to degradation when exposed to at least some portion of ultraviolet
radiation having wavelengths between approximately 190 and 400 nm
comprising: a paint or surface coating preparation including a
pigment, a binder, and a solvent that is compatible with the
pigment and the binder; a dispersion of an effective amount of
diamond nanoparticles in a paint or surface coating preparation;
and wherein at least a portion of the diamond nanoparticles have a
size greater than about 60 nm so that the diamond particles provide
ultraviolet radiation degradation resistance properties in the
dispersion.
15. The paint or surface coating preparation according to claim 14,
wherein at least a portion of the diamond nanoparticles have a size
of approximately 60-150 nm.
16. The paint or surface coating preparation according to claim 14,
wherein at least a portion of the diamond nanoparticles have a size
of approximately 100 nm.
17. The paint or surface coating preparation according to claim 14,
wherein the diamond nanoparticles comprise up to 25.0 percent by
weight of the surface coating or colorant.
18. The paint or surface coating preparation according to claim 14,
wherein the nanodiamond particles have a visible color, and wherein
the diamond nanoparticles impart a color to or modify a color of
the dispersion.
19. The paint or surface coating preparation according to claim 14,
wherein the diamond nanoparticles are modified as a result of wet
or gas phase chemical reaction(s), or chemical reactions induced
photochemically, electrochemically, mechanochemically, annealing,
or by means of a plasma, irradiation or sonic energy or modified
during a process of nanodiamond synthesis by introducing dopants
and defects to obtain diamond nanoparticles with an enhanced
ability to absorb ultraviolet radiation.
20. An article coated by the paint or surface coating preparation
of claim 14.
21. An ultraviolet radiation resistant structure that provides
resistance to degradation when exposed to at least some portion of
ultraviolet radiation having wavelengths between approximately 190
and 400 nm comprising: a substrate; a layer of ultraviolet
degradation resistant coating covering at least a portion of the
substrate, wherein the ultraviolet radiation degradation resistant
coating comprises: an effective amount of diamond nanoparticles
dispersed in a binder, wherein at least a portion of the diamond
nanoparticles have a size greater than about 60 nm so that the
diamond particles provide ultraviolet radiation degradation
resistance properties in the dispersion.
22. The structure according to claim 21, further comprising a
pigment that renders coloration to the surface coating or
colorant.
23. The structure according to claim 21, further comprising a
solvent that is compatible with the binder.
24. The structure according to claim 21, wherein at least a portion
of the diamond nanoparticles have a size of approximately 60-150
nm.
25. The structure according to claim 21, wherein at least a portion
of the diamond nanoparticles have a size of approximately 100
nm.
26. The structure according to claim 21, wherein the diamond
nanoparticles comprise up to 25.0 percent by weight of the surface
coating or colorant.
27. The structure according to claim 21, wherein the diamond
nanoparticles comprise between about 0.5 and 5.0 percent by weight
of the preparation.
28. The structure according to claim 21, wherein the nanodiamond
particles have a visible color, and wherein the diamond
nanoparticles impart a color to or modify a color of the
dispersion.
29. The structure according to claim 21, wherein the diamond
nanoparticles are modified as a result of wet or gas phase chemical
reaction(s), or chemical reactions induced photochemically,
electrochemically, mechanochemically, annealing, or by means of a
plasma, irradiation or sonic energy or modified during the process
of nanodiamond synthesis by introducing dopants and defects to
obtain diamond nanoparticles with an enhanced ability to absorb
ultraviolet radiation.
30. A pigment or additive to a surface coating or colorant
preparation that provides resistance to degradation when exposed to
at least some portion of ultraviolet radiation having wavelengths
between approximately 190 and 400 nm comprising: a dispersion of an
effective amount of diamond nanoparticles in the pigment or
additive, wherein at least a portion of the diamond nanoparticles
have a size greater than about 60 nm so that the diamond particles
provide ultraviolet radiation degradation resistance properties to
the surface coating or colorant preparation when dispersed
therein.
31. The pigment or additive according to claim 30, further
comprising a solvent that is compatible with the pigment or
additive and the surface coating or colorant.
32. The pigment or additive according to claim 30, wherein at least
a portion of the diamond nanoparticles have a size of approximately
60-150 nm.
33. The pigment or additive according to claim 30, wherein at least
a portion of the diamond nanoparticles have a size of approximately
100 nm.
34. The pigment or additive according to claim 30, wherein the
diamond nanoparticles comprise at least 0.1 percent by weight of
the pigment.
35. The pigment or additive according to claim 30, wherein the
nanodiamond particles have a visible color, and wherein the diamond
nanoparticles impart a color to or modify a color of the pigment or
additive dispersion.
36. The pigment or additive according to claim 30, wherein the
diamond nanoparticles are modified as a result of wet or gas phase
chemical reaction(s), or chemical reactions induced
photochemically, electrochemically, mechanochemically, annealing,
or by means of a plasma, irradiation or sonic energy or modified
during the process of nanodiamond synthesis by introducing dopants
and defects to obtain diamond nanoparticles with an enhanced
ability to absorb ultraviolet radiation.
37. A surface coating or colorant containing the pigment or
additive of claim 30 as a constituent thereof.
38. A method of imparting resistance to degradation due to exposure
to ultraviolet radiation to a surface coating or colorant
preparation when exposed to at least some portion of ultraviolet
radiation having wavelengths between approximately 190 and 400 nm
comprising: providing an effective amount of diamond nanoparticles,
wherein at least a portion of the diamond nanoparticles have a size
greater than about 60 nm; providing a surface coating or colorant
preparation; dispersing the nanodiamond particles into the surface
coating or colorant preparation, so that the diamond particles
provide ultraviolet radiation degradation resistance properties to
the surface coating or colorant preparation when dispersed
therein.
39. The method according to claim 38, wherein at least a portion of
the diamond nanoparticles have a size of approximately 60-150
nm.
40. The method according to claim 38, wherein at least a portion of
the diamond nanoparticles have a size of approximately 100 nm.
41. The method according to claim 38, wherein the diamond
nanoparticles comprise at least 0.1 percent by weight of the
surface coating or colorant.
42. The method according to claim 38, wherein the nanodiamond
particles have a visible color, and wherein the diamond
nanoparticles impart a color to or modify a color of the surface
coating or colorant.
43. The method according to claim 38, wherein the diamond
nanoparticles are modified as a result of wet or gas phase chemical
reaction(s), or chemical reactions induced photochemically,
electrochemically, mechanochemically, annealing or by means of a
plasma, irradiation or sonic energy or modified during the process
of nanodiamond synthesis by introducing dopants and defects to
obtain diamond nanoparticles with an enhanced ability to absorb
ultraviolet radiation.
44. A polymer composite material exhibiting resistance to
degradation by exposure to at least some portion of ultraviolet
radiation having wavelengths between approximately 190 and 400 nm
comprising: a dispersion of an effective amount of diamond
nanoparticles in the polymer composite, wherein at least a portion
of the diamond nanoparticles have a size greater than about 60 nm
so that the diamond particles provide ultraviolet radiation
degradation resistance properties to the polymer composite.
45. The polymer composite according to claim 44, further comprising
a solvent that is compatible with the polymer composite.
46. The polymer composite according to claim 44, wherein at least a
portion of the diamond nanoparticles have a size of approximately
60-150 nm.
47. The polymer composite according to claim 44, wherein at least a
portion of the diamond nanoparticles have a size of approximately
100 nm.
48. The polymer composite according to claim 44, wherein the
diamond nanoparticles comprise at least 0.1 percent by weight of
the polymer composite.
49. The polymer composite according to claim 44, wherein the
nanodiamond particles have a visible color, and wherein the diamond
nanoparticles impart a color to or modify a color of the polymer
composite.
50. The polymer composite according to claim 44, wherein the
diamond nanoparticles are modified as a result of wet or gas phase
chemical reaction(s), or chemical reactions induced
photochemically, electrochemically, mechanochemically, annealing or
by means of a plasma, irradiation or sonic energy or modified
during the process of nanodiamond synthesis by introducing dopants
and defects to obtain diamond nanoparticles with an enhanced
ability to absorb ultraviolet radiation.
51. The polymer composite according to claim 44, wherein the
composite is cured to a solid state.
52. The polymer composite according to claim 44, applied to a UV
transparent free standing support structure.
53. The polymer composite according to claim 44, wherein the free
standing support structure comprises glass.
54. The polymer composite according to claim 44, wherein the
polymer composite is sandwiched between two sheets of glass.
Description
CROSS REFERENCE TO RELATED DOCUMENTS
[0001] This application is related to and claims priority benefit
of Provisional Patent Application No. 60/712,507 filed Aug. 30,
2005 to Shenderova, et al.; and is a continuation-in-part of U.S.
patent application Ser. No. 11/338,527, filed Jan. 24, 2006 to
Kuznetsov et al., which claims priority benefit of U.S. Provisional
Patent Application No. 60/646,783, filed Jan. 25, 2005; and is also
a continuation-in-part of U.S. patent application Ser. No.
10/936,743, filed Sep. 8, 2004 to McGuire, et al., which claims
priority benefit of U.S. Provisional Patent Application No.
60/501,646 filed Sep. 9, 2003. This application is also related to
PCT Application No. PCT/US2006/033626, filed of even date herewith
to Shenderova, et al. and designating the United States entitled
"Nanodiamond UV Protectant Formulations". Each of the applications
listed above are hereby incorporated by reference.
COPYRIGHT NOTICE
[0002] A portion of the disclosure of this patent document contains
material which is subject to copyright protection. The copyright
owner has no objection to the facsimile reproduction of the patent
document or the patent disclosure, as it appears in the Patent and
Trademark Office patent file or records, but otherwise reserves all
copyright rights whatsoever.
BACKGROUND
[0003] Many materials including natural materials such as wood and
synthetic materials, such as plastics, rubbers, paints, varnishes,
adhesives, sealants and the like need to be protected against
photochemical degradation when used outdoors or otherwise exposed
to ultraviolet radiation (UVR) from the sun or when in the presence
of artificial UVR sources. Ultraviolet (UV) light can initiate
chemical reactions in natural and synthetic materials and products,
that result in discoloration and loss of chemical and physical
properties. UV stabilizers are added to the material or a coating
applied to the surface to reduce the photochemical degradation. The
types of light or UV stabilizers currently used are UV absorbers
that act by shielding the material from ultraviolet light or
hindered amine (or amid) light stabilizers (HALS) that act by
scavenging the radical intermediates formed in the photo-oxidation
process. Often hindered amines and UV absorbers are used together
to provide a level of stability which is higher than would be
provided by using either type of stabilizer by itself. It has been
reported that the most effective screeners are those with the
highest and broadest absorbance in both the UVB (290-320 nm) and
UVA (320-400 nm) ranges of the UV spectrum.
[0004] Currently both organic and inorganic UV screeners used in
plastics, paints, varnishes and other materials are commercially
available. Organic UV absorbers are used typically at 1 to 3% of
binder solids, depending on coating thickness. Examples of organic
UV absorbers include hydroxyphenyl-benzotriazol, benzophenone and
hydroxyphenyl-triazine. In the case of very prolonged exposure to
UV radiation (sunlight or light from artificial sources), however,
organic UV absorbers slowly degrade and so lose their protective
effect. The effects of weathering (humidity, high temperatures) and
the like may cause a loss of UV absorber through diffusion and
leaching.
[0005] Inorganic UV absorbers, such as, for example, titanium
dioxide, cerium dioxide or zinc oxide do not photochemically
degrade. Such inorganic particles have been used to provide more
scratch-resistance and UV-protection in transparent coatings. The
use of large alumina particles can cause the transparent coating to
exhibit an undesirable hazy appearance. Because of the high surface
area of titanium dioxide, cerium dioxide and zinc oxide
nano-particles and the potential for photochemically induced
reactions, there is possible photochemical damage and degradation
of the organic matrix surrounding the inorganic UV absorbers. This
can result in loss of adhesion between the coating and substrate.
This degradation must then be addressed by, for example, using
inorganic binders.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] Certain illustrative embodiments showing organization and
method of operation, together with objects and advantages may be
best understood by reference detailed description that follows
taken in conjunction with the accompanying drawings in which:
[0007] FIG. 1 is a diagram depicting a UV protecting coating
applied to a substrate in a manner consistent with certain
embodiments of the present invention.
[0008] FIG. 2 is a generalized flow chart depicting a coating
process consistent with certain embodiments of the present
invention.
[0009] FIG. 3 illustrates the light transmission for Ch I6
nanodiamond (ND) dispersed in de-ionized (DI) water at six
different concentrations starting with a 0.1 wt % ND suspension
diluted in half for all subsequent measurements.
[0010] FIG. 4 illustrates UV-VIS (ultraviolet to visible)
absorbance spectra of 0.17 wt % of fractions of different sizes for
two types of nanodiamond particles (heat treated Ch St and Kr-b)
dispersed in DI water.
[0011] FIG. 5 illustrates UV-VIS transmission spectra of DI water
containing 0.17 wt % nanodiamond prepared using fractions of
different sizes for two types of nanodiamond particles (heat
treated Ch St and Kr-b) dispersed using an ultrasonic horn.
[0012] FIG. 6 illustrates UV-VIS absorbance spectra of nanodiamond
films obtained by drying of nanodiamond water suspensions on quartz
substrates. Suspensions of 250 nm Ch-St ND and 25 nm particle size
fraction of Ch I6 sample were used for film preparation.
[0013] FIG. 7 illustrates the increase in the UV-VIS absorbance of
yellow exterior acrylic paint (DuraCraft.TM.) after the addition of
0.4 wt. % nanodiamonds to the un-dried paint. The spectrum was
taken with reference to an identical sample without ND
addition.
[0014] FIG. 8 illustrates the increase in the UV-VIS absorbance of
a polyurethane Clear Satin finish after the addition of 1 wt. %
(solid triangles) and 2 wt. % ND (solid line) to the un-dried
finish. The spectra were taken with reference to an identical
sample without ND addition. Ch I6 ND was used.
[0015] FIG. 9 illustrates the increase in the UV-VIS absorbance of
water-based polyacrylic finish after the addition of a water
dispersion of Ch Oz resulting in 4 wt. % of ND in the dried finish.
The spectrum was taken with reference to an identical sample
without ND addition.
[0016] FIG. 10 illustrates the relative increase in the 45.degree.
UV-VIS reflectance of wood coated with polyacrylic finish
containing 4 wt. % Ch Oz in the dried finish. The reflectance is
compared with the spectra of an identical sample without ND
addition.
[0017] FIG. 11 illustrates the increase in the UV-VIS absorbance of
polyimid films on glass substrates containing 3 wt. % of three
different types Ch ND particles in the dried films. The spectra
were taken with reference to an identical sample without ND
addition.
[0018] FIG. 12 illustrates light transmission as a function of
agglomerate size at two particular wavelengths from the UV
spectrum.
DETAILED DESCRIPTION
[0019] While this invention is susceptible of embodiment in many
different forms, there is shown in the drawings and will herein be
described in detail specific embodiments, with the understanding
that the present disclosure of such embodiments is to be considered
as an example of the principles and not intended to limit the
invention to the specific embodiments shown and described. In the
description below, like reference numerals are used to describe the
same, similar or corresponding parts in the several views of the
drawings.
[0020] The terms "a" or "an", as used herein, are defined as one or
more than one. The term "plurality", as used herein, is defined as
two or more than two. The term "another", as used herein, is
defined as at least a second or more. The terms "including" and/or
"having", as used herein, are defined as comprising (i.e., open
language).
[0021] Reference throughout this document to "one embodiment",
"certain embodiments", "an embodiment" or similar terms means that
a particular feature, structure, or characteristic described in
connection with the embodiment is included in at least one
embodiment of the present invention. Thus, the appearances of such
phrases or in various places throughout this specification are not
necessarily all referring to the same embodiment. Furthermore, the
particular features, structures, or characteristics may be combined
in any suitable manner in one or more embodiments without
limitation.
[0022] The term "or" as used herein is to be interpreted as an
inclusive or meaning any one or any combination. Therefore, "A, B
or C" means "any of the following: A; B; C; A and B; A and C; B and
C; A, B and C". An exception to this definition will occur only
when a combination of elements, functions, steps or acts are in
some way inherently mutually exclusive.
[0023] For purposes of this document, the prefix "nano" as used,
for example in "nanoparticle" is intended to refer to particles
having length in at least one dimension in the range of
approximately 1-1000 nanometers. However, in some particular cases,
the length scale for achieving the novel properties and phenomena
consistent with certain embodiments of the present invention may be
less than 1 nanometer or be slightly larger than 1000
nanometers.
[0024] For purposes of this document, the terms UV absorbers,
filters, sun blocks, UV protectants, UV screeners, UV attenuation,
and the like will generally be used interchangeably without regard
for any particular mechanism that causes the material to behave to
protect against ultraviolet radiation, except in the context of a
particular theorized mechanism that provides the exhibited
characteristics. It will be recognized by those skilled in the art
that various mechanisms may operate in such products to produce the
desired effect including light reflection, dispersion, scattering,
and absorption. Any presentation of theory of the UV protection
mechanism is presented to explain the inventors' current
understanding of the operational mechanism and is not to be
considered limiting in any way, since at this writing such
information may only constitute unproven theory.
[0025] As used herein, the term "binding matrix" or "binder" is
defined as a substance within which the nanodiamonds are contained
or suspended. In general, paints, primers, varnishes and other
coatings involve three main constituents--binder, pigment and
solvent. Diluants and various additives and fillers may also be
used in many coating formulations in order to obtain a suitable
viscosity and render additional properties of the additives to the
coating. Although there is no pigment in most clear coatings and no
solvent in some coatings designed to produce thick films, all three
main constituents are commonly present in the different types of
organic coatings. In some instances, actual binding of the
particles may take place only after the binder is cured. Examples
include, but are not limited to epoxies, paints (the term to
include primers), resins, plastics or other polymer coatings. The
term "cure" as used herein is used to refer to a drying,
solidification or other curing or setting process. For example, a
paint may cure by drying (evaporation of solvent), whereas an epoxy
may cure by setting in accordance with a chemical bonding process.
Generally, in the case of wet binding matrices, a cured matrix will
also achieve a degree of dryness. However, certain binding matrices
may be dry upon application (e.g., in a powder form) which cures by
heat or other influences to form a coating without being in a wet
or liquid state. In such cases, the term "binding" in "binding
matrix" refers to the particles being bound upon curing.
[0026] Embodiments consistent with the present invention utilize
nanoparticles of diamond. In order to understand this discussion,
it is important to have an understanding of the accepted
terminology that will be used herein when discussing particle size.
The term "primary particle size" (PPS) is the size of a smallest
primary structure in a system. This size distribution is typically
rather narrow and depends on the particle synthesis conditions.
Most suppliers of nanoparticles list only primary particle size in
their product specification. This particle size is typically
defined from x-ray diffraction pattern, Scanning-Electron
Microscopy (SEM), High-Resolution Transmission-Electron Microscopy
(HRTEM) images or calculated from Brunauer, Emmett and Teller (BET)
surface area measurements.
[0027] However, the primary particles can form aggregates or
agglomerates due to their high surface energy or
fabrication/processing conditions. The size of the aggregates is
referred to as the "aggregate" or "agglomerate" size herein to
clearly call out the distinction. The term "particle size" (PS) is
used to generically refer to either PPS or agglomerate size or a
size of a combination of agglomerates and primary particles.
[0028] Agglomerate size can be measured in a number of ways (e.g.,
SEM for dry powder forms or unimodal analysis of photon correlation
spectroscopy data for relatively transparent solutions) and often
can be tens or hundreds of times bigger than the PPS. For clarity
"primary particle size" or "agglomerate size", will be explicitly
called out when appropriate. The term nanodiamond (ND) or diamond
nanoparticles is used for submicron sized particles and may include
both or either primary particles and particles formed by
agglomerates of the primary particles. The term nanodiamond can
also include 1- and 2-dimensional diamond structures such as rods,
wires, walls, sheets, flakes, etc. with smallest dimension less
than 500 nm.
[0029] For purposes of this discussion, particle size and
agglomerate size was measured in a variety of ways including using
unimodal analysis of photon correlation spectroscopy data (in this
case, by setting the spectrometer to provide output in the unimodal
mode) for dispersions in relatively transparent liquids. This
measurement technique is rapid and has been found to provide
consistent measurements compared to other techniques, and thus,
measurements presented herein are based upon such technique when
relatively transparent liquids are analyzed, but other measurement
techniques (e.g., SEM, HRTEM) will yield similar results and can
also be used when such techniques are more suitable.
[0030] For purposes of the present discussion, the term
"degradation" is intended to encompass all types of degradation of
compositions resulting from exposure to UV radiation (including,
but not limited to, color fading or bleaching, and/or loss of
adhesion and/or loss of physical properties). Use of this term
encompasses both the material that is used as a coating or polymer
composite fabricated by means of vacuum forming, blow molding,
injection molding, hot press molding, and extrusion to name a few,
or a surface being treated with the coating or colorant. The term
"coating" is used as a generic term for surface coatings and the
term "colorant" is used to embrace dies, pigments, stains and the
like used primarily to impart coloration.
[0031] In accordance with certain embodiments consistent with the
present invention, nanodiamond (ND) particles are used to absorb,
scatter, reflect or otherwise inhibit the transmission of UV
radiation to and absorption by natural and synthetic materials such
as wood, polymers, dyes and pigments (including dyes, pigments,
binders, etc. forming a part of the coating). While all aspects of
the mechanism for the absorption of UV by nanodiamond particles may
not currently be fully understood, throughout this document various
theoretical aspects of this action are interjected in order to
better teach the various embodiments of the invention as currently
understood. However, it is to be fully understood that such
discussions of the theory as to why ND particles behave in this
manner is not to be considered limiting on embodiments of the
present invention. That is, the claimed inventions are not bound by
any theory presented herein, and disclosures of theory should be
considered just that--theory.
[0032] Nanodiamond UV absorption spectra depend on ND concentration
and a number of physical and chemical properties of the ND
particles such as particle size, physical state, composition, and
surface chemical group. ND particles can be modified as a result of
wet or gas phase chemical reaction(s), or chemical reactions
induced photo-chemically, electrochemically, mechanochemically, or
by means of a plasma, irradiation or sonic energy or other means to
obtain ND particles with an enhanced ability to absorb, scatter and
reduce UV radiation.
[0033] In certain embodiments consistent with the invention,
compounds and methods are provided to develop a new class of UV
protection compositions. In other embodiments, particular UV
protection compositions are provided. More particularly, diamond
nanoparticles are used to formulate UV protective compositions such
as paints (including primers), shellacs, lacquers, enamels,
colorants, varnishes, coatings, plastics, rubbers, glasses, fibers,
photographic papers, waxes, greases, oils and other
compositions.
[0034] For example, in accordance with certain embodiments, in
plastics compositions diamond nanoparticles are used to formulate
UV protective compositions for such substrates as polycarbonate and
polycarbonate blends, polyesters, unsaturated polyesters, polyester
fibers, polybutylene terephthalate (PBT), polyethyleneterephthalate
(PET), acrylics, polyamides, polyamide fibers, polyacetal,
polyurethanes, styrenics and other plastics and coatings. These
plastics are commonly used in applications exposed to UV light such
as interior and exterior automotive parts, lighting, sunglasses,
sheet glazing, window glazing, lawn and garden equipment, business
machine housings--computers, telephones, telecom equipment housing,
packaging (soft drinks bottles), appliances, toys, signage,
interior auto fabrics (e.g. seatbelts), sporting goods, sporting
apparel, outdoor fabrics (awnings, flags, etc.), carpets, textiles,
door and window hardware, boats, bathroom shower stalls, cultured
marble, polymer concrete, adhesives, shoe soles, sealants,
furniture cushioning, glass windows and other applications.
[0035] In certain embodiments consistent with the invention,
compounds and methods are provided to develop a new class of
coatings and their pigmented versions, paints, possessing UV
protection property including solvent-based coatings--materials
that contain or are soluble in organic solvents and water-based
coatings--materials that dissolve in or are dispersed in water.
Solvent-based coatings include, but are not limited to, oils and
oil based paints, shellacs, varnishes, enamels and lacquers. Drying
oils, obtained chiefly from vegetable sources, are examples of
oils, with linseed oil and tung oil being among the most common.
Other polymerizing oils are also used for protective coatings.
Varnishes are clear resin-containing finishes that dry by reaction
of the binder in combination, usually, with solvent evaporation.
Varnishes are also produced with vehicles including oleoresinous
binders, alkyd resins and urethane resins. Enamels are pigments
dispersed in varnishes or resins that dry by reaction and not by
solvent evaporation alone. Examples of enamel binders are the
alkyds, the epoxies, the polyurethanes and the acrylics. Lacquers
and shellacs are coatings in which the binder is dissolved in
organic solvents and drying occurs solely by evaporation of the
solvents. Examples of lacquers include vinyl and acrylic lacquers.
Such materials are collectively referred to as "coatings" herein.
This designation is without regard for the fact that such
"coatings" often penetrate the surface of certain materials in use
(e.g., oil coatings commonly soak into the surface of wood). By
dispersing nanodiamonds in the corresponding vehicle for a coating,
UV protection properties, or enhancement thereof, can be
achieved.
[0036] In accordance with certain embodiments consistent with the
present invention coatings containing nanodiamonds in a pure phase
or dispersed in polymer matrix or other binding matrix can be used
as UV protecting material.
[0037] FIG. 1 depicts a substrate 10 coated with an UV absorbing
coating consistent with certain embodiments. In this illustration,
substrate 10 is coated with coating 12 which is made up of a
binding matrix 14 containing primary particles and/or agglomerates
of tightly-bond nanodiamond particles (i.e., particles) such as 18
including at least two primary nanodiamond particles in the
agglomerate. The binding matrix may also carry aggregates of
loosely-bond diamond particles such as those depicted as 22, in
certain embodiments. The coating 12 may be a polymer matrix such as
polymethylmethacrylate (PMMA), polytetrafluorethelyne (PTFE)),
polycarbonate, polystyrene, polyurethane, polyimide, acrylics, a
paint or epoxy coating, or resin, etc. and can be applied to the
substrate using any number of techniques. Use of nanodiamond is
intended for both protecting the substrate 10 from UV damage as
well as to protect dyes, pigments or binder within the coating 12
from bleaching and photodegradation in certain embodiments of the
invention.
[0038] In certain embodiments, a coating containing nanodiamond
particles can be applied either on an outer or inner surface of a
UV transparent free standing support structure such, as for example
window glass, providing UV protection of the interiors behind the
support (for example, interior of a house or an automobile and
other embodiments) on the side opposite to the source of UV
radiation. Similar, nanodiamond particles can be incorporated to
such support structure or be enclosed between two support
structures.
[0039] Molded polymer composites with nanodiamonds can be used
without a special substrate, in order to form housings, covers,
containers or enclosures. Different methods of curing (such as
thermal curing, for example) can be used to form free-standing
structures (e.g., molded parts) with UV protection properties.
[0040] Candidates for use as the binding matrix also include, but
are not limited to: elastomers, methacrylic, phenolic, vinyl,
silicone, polyester, polyurethane foam (PUF), PDMS
(polydimethylsiloxane), conducting polymers, vinyl polymers, phenol
formaldehyde, neoprene, rubber, silicone rubber compounds,
polypyrrole, polyaniline, polyacetylene, polythiophene,
poly-p-phenylene, polyacrylthiophene,
poly-p-phenylene-benzo-biz-thiozole (PBT), butadieneacrylonitrile,
fibers, ceramics (e.g., SiO2, Al203), conductive polyethylenes
(CPE), polyethyelene compounds with polyisobutylene, ethylene ethyl
acrylate copolymers, extruded polystyrene foam (e.g.,
Styrofoam.TM.), and expanded polyvinylchloride (e.g., Spongex.TM.),
to name but a few examples.
[0041] The selection of the polymer matrix is not believed to be
critical, and the specific application will generally dictate which
binding matrix is used. For any matrix the nanodiamond particles
should preferably, but not necessarily, be uniformly or near
uniformly dispersed in the binding matrix.
[0042] As a mechanism of fabrication of coatings containing
nanodiamond particles dispersed in a polymer matrix, different
techniques can be used that include, for example, dipping, roller
coating, brushing, spray techniques, fluidized bed, spin-on coating
of a polymer suspension and wiping to mention just a few. The spray
techniques include paint spray, electrostatic spray, hot melt
spray, high velocity high temperature spray, thermal spray, plasma
spray, and ultrasonic spray. Spray techniques may be a practical
way to synthesize coatings on large free-standing surfaces. Using
different spray technique the coatings incorporated nanodiamonds
can be applied over large free-standing surfaces (e.g., an aircraft
body), in applications for protection of civilian or military
aircraft, ships or other transportation vehicles or structures.
[0043] FIG. 2 generally shows a process 30 for both manufacture of
the coating material and application of the coating starting at 34.
At 38, operative quantities of nanodiamond particles, which may be
functionalized or processed with any of the above variations, are
blended into the binding matrix which serves as a carrier and
binder for the nanodiamond particles. The concentration of
nanodiamonds can be determined experimentally to achieve a desired
degree of UV absorption, as will be described in connection with
the experiments that follow, but may generally be in the range of
0.1-25.0% by weight or more preferably in the range of 0.5-5.0% by
weight.
[0044] At 42, the coating can be applied to the article to be
coated (i.e., the substrate--which may, for example be a panel of
an aircraft or automotive part or a part of a building or other
construction). Any of a number of application processes is
appropriate for this process. If required, depending upon the
binding matrix, the coating can then be cured or dried at 44,
depending upon the technology used.
[0045] The curing process 44 may be a negligible part of certain
processes while in other processes curing may be a more extensive
and may involve, for example, application of heat or exposure to
cure accelerants or other catalysts.
[0046] In an alternative embodiment, rather than applying the
coating to an article or substrate at 42, the blend can be molded
or otherwise fashioned into a free-standing article (e.g., a molded
transportation vehicle part) at 42. In either event, the process
ends at 48.
[0047] Use of diamond particles for UV protection can be very
beneficial. Bulk diamond has a refractive index of approximately
2.4. Thus diamond particles scatter light very efficiently. Such
diamond particles have been discovered to be strong absorbers of
UVB and UVA radiation, as well as UVC radiation. Thus, ND particles
provide a single physical absorber of UVA, UVB and UVC radiation to
avoid the complications connected with processing of a UVR
protection composition when combining different type of particles
or organic absorbers (which does not preclude use of such additives
to further enhance the UV protective qualities of a given
composition).
[0048] While a complete understanding of the strong absorption in
UV spectra of radiation by nanodiamond particles is yet to be
revealed, possible mechanisms theorized for causing the absorption
include absorption by the atoms with sp.sup.2 bonding terminating a
part of the particles surfaces; the surface groups involving other
elements in addition to carbon; and absorption by internal defects
in the bulk of diamond particles followed by photoluminescence and
other phenomena. For example, there are several defect centers due
to dopant atoms (N, B and other elements), self-interstitials,
vacancies, complexes of the above, complexes of the charged
defects, dislocations that cause absorption and photoluminescence,
particularly at wavelengths shorter than 420 nm. That means that UV
light is absorbed by these structural features and then is
reemitted at a longer wavelength, primarily in the visible range of
light for the case of photoluminescence.
[0049] While the fundamental absorption edge of bulk diamond is at
a wavelength of about 220 nm (the band-gap of diamond is 5.5 eV),
there are reports of effective band gaps in ultradispersed diamond
particles within the range of .about.3 eV. Dopants, surface states,
internal defects and atomically sharp grain boundaries observed
between primary diamond particles are all believed to contribute to
the formation of the sub-bands within a fundamental band gap and
thus cause the UV absorption at wavelengths longer than those
corresponding to the fundamental band-gap.
[0050] The photoluminescence and other processes of conversion of
absorbed UV radiation into emitted light in diamond particles are
believed to be possibly due to defects that are present naturally
as a result of material formation/processing or created by
subsequent irradiation (for example, electron, ion or other types
of irradiation) or obtained by subsequent annealing or be created
by other means. In accordance with certain embodiments, diamond
particles that actively absorb UVC, UVB, and UVA radiation can be
used in UV protection compositions for paints, lacquers, varnishes,
plastics and the like with sunscreen attributes alone or in
combination with other UV filters.
[0051] There are also other benefits of using diamond particles as
UV filters. Diamond particles possess a chemically inert core that
provides additional benefits for its use in UV protection
compositions in outdoor and indoor use. ND is resistant to moisture
and acid and basic environments. ND is thermally resistant and may
add to coatings other useful properties such as increased
degradation temperature and improved flammability, increased
adhesion, improved resistance to wear, scratch resistance,
durability and the like. This can be a significant advantage in
certain applications when compared to other UV filters. UV light
that is still getting through the coating generates free radicals
that can cause the coating material degradation. Since diamond
nanoparticles are reported to scavenge free radicals a further
benefit may be obtained in protecting coatings and structures from
being damaged or bleached as a result of UV-induced radical chain
reactions. The surface of the diamond particles can be easily
functionalized with a very broad variety of different chemical
functional groups that can facilitate dispersion of diamond
particles in different compositions.
[0052] Nanodiamond particles can be utilized in a number of ways,
for example:
[0053] in a method of protecting a surface or material from
ultraviolet radiation by applying to the surface or material a
formulation including an acceptable solvent or carrier and
nanodiamonds or mixture of nanodiamonds with other organic and
inorganic UV absorbers, light stabilizers, antioxidant agents and
other additives;
[0054] in a method of protecting a surface from ultraviolet
radiation by topically applying to the surface a formulation having
an acceptable solvent or carrier, a paint, a polish, a dye, or a
coating material containing nanodiamonds or a mixture of
nanodiamonds with other organic and inorganic UV absorbers, light
stabilizers, antioxidant agents and other additives;
[0055] in a method of protecting a surface or an object from
ultraviolet and other radiation by introducing an aerosol
containing nanodiamonds or a mixture of nanodiamonds with other
organic or inorganic UV absorbers or gaseous carrier containing
nanodiamonds or a mixture of nanodiamonds with other organic or
inorganic UV absorbers, light stabilizers, antioxidant agents and
other additives;
[0056] in a method of protecting a material by incorporating
nanodiamonds or a mixture of nanodiamonds with other organic or
inorganic UV absorbers, light stabilizers, antioxidant agents and
other additives in structures formed by molding, extrusion or other
similar means;
[0057] in a method of protecting a material by incorporating
nanodiamonds or a mixture of nanodiamonds with other organic or
inorganic UV absorbers, light stabilizers, antioxidant agents and
other additives in a surface layer of a structure formed by
molding, extrusion or other similar means.
[0058] Diamond nanoparticles can be produced by several means.
Vapor phase formation such as chemical vapor deposition, ion
irradiation of graphite, chlorination of carbides, and techniques
using shock wave energies are some of the several possible methods
to produce such diamond particles. It should be mentioned that
besides diamond particles of spherical form or irregular-shaped
particles other 1- and 2-dimensional nanodiamond structures had
been fabricated such as ND rods, wires, walls, sheets, flakes, etc.
which can also be used in UV protecting compositions (on methods of
synthesis of these structures see O, Shenderova and G. McGuire,
Types of Nanodiamonds, book chapter in "Ultrananocrystalline
diamond: Synthesis, Properties and Applications", Editors: O,
Shenderova, D. Gruen, William-Andrews Publisher, 2006).
[0059] The shock wave method of nanodiamond particle production
includes graphite transformation by a shock wave (the primary
particle size for most popular current commercial products produced
by this method is about 25 nm) and nanodiamond produced by
detonation of carbon-containing explosives (the primary particle
size produced by this method is approximately 3-5 nm in most
currently available commercial products). Primary nanodiamond
particles produced by detonation of carbon containing explosives
form both tightly bonded aggregates (possibly fused during the
detonation process) and loosely bonded aggregates.
[0060] As will be described with reference to various publications
below, which are hereby incorporated by reference, diamond
nanoparticles can be produced by several means, and which will
result in varying primary particle sizes and varying agglomeration
characteristics (see O. Shenderova and G. McGuire, Types of
Nanodiamonds, book chapter in "Ultrananocrystalline diamond:
Synthesis, Properties and Applications", Editors: O. Shenderova, D.
Gruen, William-Andrews Publisher, 2006). Isolated nanocrystalline
diamond particles with characteristic sizes of several tens of
nanometers can be monocrystalline or polycrystalline.
Monocrystalline particles are obtained by processing of
micron-sized diamond particles, which are, in turn, a byproduct of
natural diamond or synthetic high pressure high temperature (HPHT)
diamond synthesis. Synthetic diamond particles with sizes below
.about.50 microns represent the raw material for making micron and
sub-micron diamond size particles.
[0061] The processing of micron sized diamond particles to smaller
fractions includes micronizing, purification and grading of the
powder. The polycrystalline nanodiamond powder can be processed
from micron sized polycrystalline diamond particles obtained by
shock wave synthesis. Under suitable conditions, explosively
produced shock waves can create high pressure-high temperature
conditions in confined volumes for a sufficient duration to achieve
partial conversion of graphite into nanometer-sized diamond grains
(.about.20 nm) which compact into micron-sized, polycrystalline
particles. The processing of micron sized diamond particles to
smaller fractions includes micronizing, purification and grading of
the powder. For example, polycrystalline or monocrystalline
nanodiamond particles described above are sold by Microdiamant AG,
Switzerland. Range of particle sizes provided by Microdiamant
include the smallest fraction sizes 0-50 nm (median size: .about.25
nm), 0-100 nm (median size 50 nm), 0-150 nm (median size 75 nm) and
larger fractions of polycrystalline diamond. For monocrystalline
natural diamond particles the size ranges include 0-250 nm (average
size 125 nm) fraction and larger size fractions. Frenklach and
co-workers [Frenklach M, Kematick R, Huang D, et al., Homogeneous
nucleation of diamond powder in the gas phase, J. Appl. Phys 66,
395-399, 1989] studied nucleation and growth of nanodiamond powder
directly in the vapor phase in a substrate-free low-pressure
microwave-plasma chemical vapor deposition (CVD) reactor. The
particles were collected downstream of the reaction zone on a
filter within the tubular flow reactor and subjected to wet
oxidation to remove non-diamond carbon. The homogeneous diamond
nucleation took place when a dichloromethane- and
trichloroethylene-oxygen mixture was used as source material. The
particles had crystalline shapes with an average particle size of
around 50 nm. A mixture of diamond polytypes were observed in the
powder. Frenklach et al. [Frenklach M., Howard W., Huang D., et
al., Induced nucleation of diamond powder. Appl. Phys. Lett., 59,
546, 1991.] also studied the effects of heteroatom addition on the
nucleation of solid carbon in a low-pressure plasma reactor. The
addition of diborane (B.sub.2H.sub.6) resulted in substantial
production of diamond particles, 5 to 450 nm in diameter, under the
same conditions that show no diamond formation without the presence
of diborane. Recently, spherical, rather monodispersed diamond
particles with diameters of different fractions in the range from
150 to 600 nm have been synthesized in the gas phase by
multi-cathode direct current plasma activated CVD [Lee J K, Baik Y
J, Eun K Y, et al., Synthesis of diamond spheres Chem. Vap. Depos.,
10, 133, 2004]. The internal structure of a spherical particle is
made of nanocrystalline diamond grains .about.30 nm in size. Other
methods of nanodiamond formation include ion irradiation of
graphite, chlorination of carbides, and several other possible
methods to produce such diamond particles.
[0062] One of the most popular commercial nanodiamond products is
nanodiamond produced by detonation of carbon-containing explosives
(the primary particle size produced by this method is approximately
3-5 nm in most currently popular commercial products, although
monocrystallite particle sizes up to 50 nm can be also observed).
Primary nanodiamond particles produced by detonation of carbon
containing explosives form both tightly bonded aggregates (possibly
fused during the detonation process) and loosely bonded aggregates.
Recently, using stirred-media milling technique, it was shown
possible to de-agglomerate detonation nanodiamond down to their
primary particle sizes, 4-5 mm. The slurries of 4-5 nm detonation
nanodiamond particles can be resistant to agglomeration for a long
period of time [A. Kru{umlaut over ( )}ger, F. Kataoka, M. Ozawa,
et al., Unusually tight aggregation in detonation nanodiamond:
identification and disintegration, Carbon 43 (8), 1722-1730, 2005].
As was mentioned above, different means of enhancement of UV
absorption by different types of nanodiamond particles can be
achieved. The above documents are hereby incorporated by reference
herein.
[0063] The experimental examples presented herein generally used
agglomerates of detonation diamond nanoparticles, and the sizes
presented are generally sizes of such nanoparticles. However, as
noted above, primary particles of similar sizes are expected to
perform in a similar manner. Hence, the present invention is not
limited to agglomerates of smaller primary particles, but also
encompasses use of larger primary particles than those of the
detonation nanodiamond (DND) used in the experiments.
[0064] Commercially obtained nanodiamond powder produced by a
detonation process, DND, is a polydispersed powder of particles
mostly within the 10-1000 nm size range. These polydispersed
nanodiamond particles can be fractionated into fractions with small
and large particles with relatively narrow particle size
distributions, with the size represented herein being measured
using unimodal analysis of photon correlation spectroscopy data.
These are the sizes of nanodiamond fractionated particles, largely
aggregates that are used throughout this discussion unless
otherwise designated. The sizes are measured by the photon
correlation spectroscopy method when particles are dispersed in a
liquid media or otherwise measured using SEM. The particle sizes
referenced are thus a type of average values (assuming spherical
shapes) of irregular shaped aggregate particles of diamond, as is
conventional in this field. Examples of available nanodiamond
fractionated particles include particles with 25 nm, 35 nm, 50 nm,
60 nm, 70-80 nm, 100 nm, 150 nm and larger particle sizes. Examples
of fractionation approaches include centrifugation,
ultracentrifugation, and density gradient centrifugation.
[0065] Based upon experiments conducted to date, there appears to
be several advantages of using detonation nanodiamonds as UV
filters (but this does not imply that nanodiamond produced by other
means cannot be used). These particles demonstrate strong
luminescence when excited by UV radiation, probably due to numerous
internal defects formed during particle synthesis (nitrogen-related
defects for example, since nitrogen is a constituent of the
explosives used for the synthesis). Strong UV absorption can be
also possibly attributed to the sp.sup.2 termination of a part of a
particle surface formed during subsequent particle processing. The
particles contain a wide variety of surface chemical groups such as
carboxyl, hydroxyl, amino, carbonyl and other groups some of which
may contribute to the absorption.
[0066] Additionally it is noted that detonation nanodiamonds are
intrinsically hydrophilic, thus they can form stable hydrosols. At
the same time, some of them can be dispersed in a variety of
alcohols, N-Methyl-2-Pyrrolidone (NMP) and oils (for example,
nanodiamond purified with ozone) even without additional surface
modification. Surface modification methods are also well developed
for nanodiamonds to be dispersed in polar and non-polar media. For
example, heat treatment of ND in air atmosphere at temperature
350-450.degree. C. within an hour improves its dispersivity in
water; surface fluorination in atmospheric plasma system using
fluorine-containing gases helps improve dispersivity in acetone,
chloroform, alcohols, tetrahydrofuran (THF) and some oils.
Dispersion of nanodiamonds in different media can be done using
ultrasonic energy, mixing, blending, shaking, magnetic stirring and
other methods. Reduction of sizes of nanodiamond aggregates can be
done by grinding, milling, treatment in atmospheric or
sub-atmospheric pressure plasma and by other methods.
[0067] According to certain embodiments consistent with the present
invention, a diamond particulate composition has UV attenuating
diamond particles with a size greater than about 60 nm and
generally less than about 1 micron. The composition can optionally
further incorporate a composition of such particles in combination
with other UV absorbing agents that can be chosen from organic
screening agents, inorganic physical screening agents and their
mixtures. The composition can comprise any UVA and UVB screening
agent, which can be used in the coatings and plastics and by
appropriate dispersion in an acceptable carrier such as a powder,
oil, gel, wax, emulsion, solvent or other uncured coating or
plastic base.
[0068] Sometimes, coatings and plastic products are preferably
visually transparent or nearly so. Detonation diamond particles
with size less than approximately 120-150 nm in diameter can
provide the advantage of forming highly uniform dispersions with a
relatively high translucency factor (at concentrations, for example
in water .about.0.1 mas s %). In addition, nanodiamond particles
might provide the advantage of requiring a smaller amount of
particulate per unit of surface as compared to other UV attenuating
materials to be protected from UV light to achieve the desired
level of protection.
[0069] According to certain embodiments, UV protection compositions
can be formulated to contain as-purified diamond particles,
functionalized diamond particles or diamond particles with attached
organic molecules that are made particularly suitable for use with
the desirable carrier, agent or solvent (liquid, solid or aerosol,
and etc.). The vehicle may be an aqueous solution, or a polar
organic solvent, alcohol, e.g. ethanol or other polar-solvent;
acetone, natural or synthetic oil; an oil-in-water emulsion; or a
water-in-oil emulsion; or a wax; and the like.
[0070] In accordance with certain embodiments consistent with the
present invention, nanodiamond-derived particles can be used as a
UV absorber and photostabilizer, including nanodiamonds produced by
detonation, shock wave, chemical vapor deposition (CVD),
high-pressure-high-temperature (HPHT), and other methods. Besides
particles, other primarily 1- and 2-dimensional nanodiamond
structures such as ND rods, wires, walls, sheets, flakes, etc. can
also be used in UV protecting compositions.
[0071] Nanodiamond particles can be, in addition, doped or modified
chemically (wet chemistry, gas phase reactions, catalytic
conversion), electrochemically, mechanochemically, sonochemically,
photochemically, by exposure to radiation and beams, by oxidation,
for example, with acids, oxygen or ozone, annealing in air or other
gas atmospheres or with plasma treatment and other methods to
enhance absorption of UV radiation by creating of structural
defects, sp.sup.2 bonded surface termination and surface functional
groups attached to the ND surface by either covalent or
non-covalent bonds. It is also possible to perform
functionalization of diamond particulate in a gas plasma
discharge.
[0072] Also, diamond particles can be modified to enhance the
stability of their dispersions in a suitable carrier or liquid,
provide chemical compatibility and assure surface adhesion of the
coatings. In addition, diamond and other carbon-based particulate
mixtures with nanodiamonds may form complexes with organic
molecules to enhance UV light absorption.
[0073] The energy of the UV radiation absorbed by diamond particles
may be converted into energy of chemical bonds, scattered,
dissipated as heat or converted into energy of photoluminescence.
The diamond nanoparticles actively scatter light as a function of
condition, particle size and shape, wavelength, polarization state,
and angle of incidence. This is expected to reduce the amount of
absorbed energy converted to heat and may provide additional
aesthetic effect by either contributing to the color or other
visible characteristics of the coatings.
[0074] According to certain embodiments consistent with the present
invention, a composition of a coating with aesthetic appeal has
diamond particles exhibiting photoluminescence, fluorescence or
phosphorescence under UV or other light due to the presence of
nitrogen and other impurities defects, N--V centers or other
structural features. The emitted light wavelength is determined by
the intrinsic diamond particle properties, excitation light and
properties of the coating composition.
[0075] According to certain embodiments of the present invention,
the formulation of coatings and plastics can be augmented with
diamond particles of a chosen color e.g., white, violet, brick or
other colors alone or in combination with other coloring agents.
Doping of ND to induce colored centers can be realized by several
means including at the stage of detonation of the explosives used
to produce the ND by the addition of materials to the explosives
that induce color variations. Doping can be also induced by
radiation and other means known in the art.
[0076] Experiments have been conducted with quantities of ND
agglomerates as low as 0.01 wt. % which have exhibited substantial
ultraviolet absorption. In commercial coatings and plastics, an
addition of perhaps as low as 0.5 wt. % or even lower may provide
beneficial enhancement to coatings and plastics for enhancement of
UV protection. Further, addition of 1-2 wt. % or greater, perhaps
as much as 3 wt. % to 5 wt. % could provide even higher benefits in
protection against UV. In some applications as high as 10-25 wt. %
or even higher is projected to be useful for providing high degrees
of UV protection, although high concentrations may contribute to
visibility of the ND particles. Of course, the appropriate
concentration of ND or similar materials can be determined
experimentally according to the base material and the desired
effect. Systematic trials of varying percentages of ND blended
uniformly as an admixture with the desired base material can be
done to determine the amount needed to achieve the desired result
for any given base material. Thus, the above ranges should be
considered as a starting point for straightforward experimental
determination of the concentration needed to achieve a desired
result. In the case of ND particles used in paint pigments or other
additives, the above percentages may be adjusted upward so as to
produce a suitable final concentration of the finished product
after addition of the additive.
[0077] As will be seen in the experimental data, there is a
surprisingly strong change in the absorption of UVR in the longer
UV wavelengths that is dependent upon the nanodiamond particle
size. This dependency is non-linear and heretofore unreported. At
lower particle sizes, the ultraviolet light absorption properties
may go unnoticed, but as particle size increases above about 60 nm,
the amount of UV absorption is observed to dramatically and
surprisingly increase at the upper end of the wavelength by a large
factor that appears to have an approximately exponential shape.
Under laboratory test conditions, transmission of UV light at 350
nm wavelength has been found to decrease by a factor of 19 when the
size of particle agglomerates is doubled from 50 nm to 100 nm (3.8%
vs. 0.2% of transmitted radiation). Transmission of UV light at 400
nm wavelength has been found to decrease by a factor of 15.8 when
the size of particle agglomerates is doubled from 50 nm to 100 nm
(14.2% vs. 0.9%). Between 60 nm and 100 nm, the light transmission
at 350 nm wavelength, transmission was decrease by a factor of 8.5
(1.7% vs. 0.2%), and at 400 nm wavelength, transmission was cut by
a factor of 10 (9% vs. 0.9%)
[0078] As particle sizes increase to the range of 125 to 150 nm and
beyond, the transmission of UV light is extremely highly
attenuated, but the particle size is such that the composition may
become more readily visible in higher concentrations and
application thicknesses. Hence, preferred ranges of particle
agglomerate sizes range from about 60 to about 150 nm, with a more
preferred agglomerate size range from about 75 to about 125 nm, and
about 100 nm being most preferred in formulations where
transparency of the particles is desirable. Higher concentrations
and larger particle sizes can be used when transparency is not an
important consideration. Particle sizes of approximately 100 nm
provide extremely good UV absorption while remaining transparent at
relatively high concentrations, and are therefore considered
approximately optimum for such applications.
[0079] In view of the above noted properties of ND, it appears that
these materials can be used not only as efficient UV radiation
absorbers, but also visible radiation absorbers. To enhance the
ability of ND to absorb UV radiation ND can be combined with an
appropriate carrier or other material. Examples of the carriers and
materials include, but are not limited to, virtually any base
medium used in known coatings and plastics. The precise quantity of
ND to be used in such formulations can be readily determined
experimentally based on the desired UV absorbing properties of the
final product and its cost, and the effect of ND on color and/or
clarity of the formulation. Based on the absorption spectra it can
be seen that formulations that contain as little as 2% mass with a
size of ND particles as added to the dispersion of about 60-100 nm
shows very substantial beneficial UV absorption.
[0080] The ranges of values for the addition of ND particles given
herein are to be considered as representative amounts provided as
guidance to further refinement and experimentation and should not
be considered absolutes or limiting. Additionally, the ranges
listed herein are to be interpreted as including every possible
smaller range within each range, and when minimum or maximum values
are provided, they are intended to be effectively unbound at the
opposite end of the range. It is additionally noted that the
mechanism and medium used to create the dispersion can result in
additional agglomeration into larger particles agglomerates and
this should be taken into consideration when developing a
formulation since both UV absorption and transparency or
translucency will be affected.
EXAMPLES
[0081] In the examples described below, ND particles produced by
explosives detonation are used to illustrate the usefulness of
nanodiamond in applications for protection from UV radiation.
Detonation nanodiamonds (DND) are synthesized at the high
pressure-high temperature conditions achieved within the shock wave
resulting from the detonation of carbon-containing explosives with
a negative oxygen balance. In this method, diamond clusters are
formed from carbon atoms contained within explosive molecules
themselves, so only the explosive material is used as a precursor
material. A wide variety of explosive materials can be used. One
example of a typical explosive is a mixture of TNT
(2-methyl-1,3,5-trinitrobenzene) and hexogen
(hexahydro-1,3,5-trinitro-1,3,5-triazine) (RDX) composed of C, N, O
and H with a negative oxygen balance (i.e. with the oxygen content
lower than the stoichiometric value required to react with the
carbon of the explosive), so that `excess` carbon is present in the
system.
[0082] The explosion takes place in an inert (non-oxidizing) to
carbon gas medium that plays the role of a coolant and is either
gas (N.sub.2, CO.sub.2, Ar or other medium under pressure) or ice
(water), so called `dry` or `wet` synthesis, correspondingly. The
product obtained by detonation, called detonation soot, contains
the diamond nano-particles along with other carbon structures. A
variety of techniques can be used to separate the ND phase from
soot, for example, by oxidizing the non-diamond carbon. A typical
average primary particle size of DND is within the size range of
3-5 nm. In the final product, DND powder, nano-diamond primary
nano-particles form tightly and loosely bonded aggregates ranging
in the largest dimension from several tens to several hundreds of
nanometers and up to micrometers. Since as-received purified
powders contain a wide variety of particle sizes, they are called
polydispersed. Polydispersed powder can be separated into fractions
with a narrower range of particle sizes by known methods (for
example, by centrifugation).
[0083] In the examples presented below, several types of DND
obtained from different vendors were used for the experiments. Some
DND were produced in a chamber containing a gas medium as the
coolant (Kr-b) and some types of DND were produced using an ice
coating around the detonation charge (Ch St, Ch Oz).
[0084] Sample Kr-b was purchased from the Institute of Biophysics,
Krasnoyarsk, Russia and was produced at Krasnoyarsk Research
Center, Russia by explosion of TNT/RDX in a CO.sub.2 atmosphere and
acid-oxidized, washed with water, and dried. Then the sample was
modified by a vendor. Modification is based on incorporation of
Na.sup.+ ions into the ND surface. This modification increases
significantly the DND dispersivity and hydrosol stability.
[0085] Ch St and Ch Oz samples were synthesized from a mixture of
TNT/RDX (40/60 wt. %) explosives using ice cooling media (purchased
from "New Technologies", Chelyabinsk, Russia). Ch St ND was
obtained by the detonation soot purification process using a
mixture of sulfuric acid with chromic anhydride treatment, washed
with water, and dried. Ch Oz ND was purified from the soot in an
ozone-flow reactor (`dry` oxidation method). The average size of
the primary particles for both samples was about 4 nm. Further
modification of the Ch St sample was performed at the vendor site.
Sample Ch St was additionally purified using ion-exchange resins,
heat treated in an air atmosphere and fractionated by
centrifugation down to 150 nm average particle size when dispersed
in water and measured using photon correlation spectroscopy (PCS).
This modified sample is called Ch I6 in the experiments below.
[0086] From several DND samples, fractions of smaller particle
sizes were produced for selected experiments. First, the initial
DND powder was dispersed in DI water using a custom made
direct-immersion horn-type ultrasound sonicator with an output
power of 100-400 W. Then, the DND hydrosol was centrifuged at
20.degree. C. using a multipurpose refrigerated centrifuge (Thermo
Electron Corporation) equipped with a 17.5-cm fixed angle rotor and
50-mL conical centrifuged tubes. Centrifugation time varied between
5 minutes and 50 minutes depending on the fraction size of
interest. G-forces varied between 1,000 g and 25,000 g. DND
particle size distributions in their hydrosols were measured by PCS
using a Beckman-Coulter N5 submicron particle size analyzer.
[0087] The surface chemistry of the samples under investigation is
very different due to different methods of purification and
modification applied to the samples. TABLE 1 summarizes the content
of surface groups of the samples studied using FTIR spectra. FTIR
spectra were obtained with a Varian 7000e FTIR spectrometer in
transmission mode with averaging over 500 spectra. A wide variety
of surface groups is observed for the ND samples under study. The
type of surface group influences the dispersivity of DND in
different solvents and materials as well as their resistivity to
agglomeration and sedimentation. For example, the most stable water
and alcohol suspensions can be formed from Ch Oz, Kr-b, and Ch I6.
Stable oil-based suspensions can be also formed based on these ND
(for example using Ch Oz and Ch I6). Surface groups of the
nanodiamonds can be changed by known reactions in order to improve
their dispersivity and resistance to agglomeration and
sedimentation in different polar and non-polar media.
[0088] The graphs illustrate absorbance (A=.epsilon.lC,
.epsilon.--extinction coefficient, l--sample thickness
C--concentration) as a function of wavelength in nanometers.
Absorbance A=log.sub.10 (I.sub.0/I), where I.sub.0 and I are
incident and transmitted intensity of the radiation at a given
wavelength. Since transmittance T=I/I.sub.0, A=1 corresponds to a
case when only 10% of the radiation was transmitted; at A=2
incident radiation is reduced 100 times. Absorbance was measured
with a Perkin-Elmer Lambda 35 UV-Vis spectrophotometer. Instrument
settings were as follows: 190-1100 nm scan range, 480 nm/min scan
speed, 1 nm data interval, 1 sec. cycle time, and 1 nm slit width.
Lamp change-over wavelength was set at 326 nm. Liquid samples were
measured by placing them in 1-cm quartz cells.
Example 1
[0089] In this series of experiments Ch I6 ND was used. The
dependence of UVR absorbance on the concentration of ND in water
was investigated. 8 mg of ND powder was dispersed in 8 ml of DI
water using sonication for 5 min. Sonication was carried out using
a sonicator equipped with a tapered titanium horn with a tip
diameter of 3 mm (Cole-Parmer.RTM. 750-Watt Ultrasonic Homogenizer
EW-04711-60, 20 kHz) that was directly immersed into the sample.
The output power was 10 W, output intensity .about.100 W/cm.sup.2.
The unimodal particle size distribution obtained using PCS
(Beckman-Coulter N5 submicron particle size analyzer) device was
180 nm. Then the suspension was diluted in half several times so
that the concentrations of the test samples were 0.1, 0.05, 0.025,
0.0125, 0.00625 and 0.003125 wt. % of DND. While ND suspensions at
0.1 wt % and 0.05 wt. % concentrations of ND were light and opaque,
suspensions starting with 0.025 wt. % concentration were
transparent and show opalescence that might be attractive for some
aesthetic-related applications.
[0090] All samples were tested at the same conditions; the sample
volume for absorption measurements was 4 ml. The UV-VIS spectra
were recorded using as a reference a quartz cell filled with pure
DI water. Pure DI water does not absorb significantly in the
wavelength range 200-900 nm.
[0091] The recorded transmission spectra are illustrated in FIG. 3.
As can be seen from the spectra, ND water suspension in the range
of concentrations of 0.025-0.1 wt. % demonstrate strong absorbance
of UVR (for example, transmission at 350 nm varies between 2.1% and
0.007% for the suspensions with 0.025 and 0.1 wt. % ND
concentrations, correspondingly). Even suspensions with lower
concentrations of ND such as 0.003125-0.0125 wt. % demonstrate
reasonable UVR absorption (for example, transmission at 350 nm
varies between 15% and 63% for the suspensions with 0.0125 and
0.003125 wt. % concentrations, correspondingly). Light absorption
by ND suspensions is much stronger in the UV region than in the VIS
region. For example, from the absorption spectra (not shown in the
figure), absorbance at 300 nm wavelength is 6.4 times higher than
at 600 mm. Also note the high transmission of the suspensions in
the VIS region for samples with concentrations lower than 0.05 wt.
%.
Example 2
[0092] In this series of experiments Ch St and Kr-b DND were used.
The purpose of this experiment was to obtain DND water suspensions
of large and small particles sizes at the same concentration by
weight for comparison of their UV shielding. Ch St was
surface-modified in order to improve its dispersivity in water. For
this, Ch St powder was placed in an open glass container then
heated at a rate of 10 degrees C./min up to 425.degree. C. in an
oven in air and then held at this temperature for 1 hour and then
cooled down within an hour down to room temperature. This helped to
obtain powder that disperses well in water, likely due to the
increased amount of oxygen-containing surface groups. Then the
sample was dispersed in DI water and fractionated using a
centrifuge to obtain fractions with average aggregate sizes of 360
nm, 190 nm, 100 nm, 60 nm and 50 nm. Dried powders of the fractions
360 nm and 190 nm were obtained by evaporating the water. The
smallest fractions of Ch St (100, 60 and 50 nm) were not dried to
avoid possible agglomeration as a result of drying. Their
concentrations were measured by first evaporating and weighing
known volumes of the suspension. Once the sample concentration was
known, it was easy to dilute a sample with a known concentration to
the target concentration.
[0093] The Kr-B sample was also fractionated using the centrifuge
to obtain 100 nm, 40 nm and 35 nm average aggregate size fractions.
It is known that Kr-B fractions do not agglomerate during drying,
so, dried powders of the 100 nm, 40 nm and 35 nm fractions of the
Kr-B were obtained by the evaporating water. The smallest
concentration of Ch St suspensions was 0.17 wt. % for 50 nm
fractions. All other samples for UV-VIS spectral analysis were
prepared at the same target 0.17 wt. % concentration by diluting
100 nm and 60 nm Ch St suspension or dissolving the necessary
amount of dried powders of DND fractions in DI water. All
suspensions were sonicated for 2 minutes. The sample preparation
procedure for UV-VIS spectroscopic analysis is the same as in
EXAMPLE 1.
[0094] Fractions 360 nm and 190 nm were light- and dark-grey,
correspondingly. Suspensions of the fractions 100 nm and below were
optically transparent, both 100 nm fractions for Ch St and Kr-B
were brownish, 60, 50, 40 and 35 nm fractions showed a transition
from light brownish to yellowish colors. The suspensions of the
smallest fractions were more transparent. FIG. 4 illustrates the
UV-VIS spectra for selected water suspensions of the fractions.
Fractions 360 nm and 190 nm show large absorbance in both the UV
and VIS spectra. Fractions 100 nm for both Ch St and Kr-B showed
rather similar spectra (the latter was not included in FIG. 4),
slightly larger absorbance was observed for the 100 nm Ch-St
sample. According to FIG. 4, the most appealing for UV shielding
compositions for transparent would be about 100 nm fractions, which
demonstrate very high UV shielding in the range 200-400 nm, while
possessing transparency in the VIS range. Larger agglomerates could
be used where transparency is not a consideration.
[0095] Also, it can be noted that the curve corresponding to the
suspension produced from the 100 nm Ch St sample is similar to the
spectrum of the suspension produced using 100 nm Kr-b, (not shown
in the Figure). It can be also noted an additional specific
absorbance shoulder between 330 nm and 400 nm wavelengths which can
be observed in FIG. 4 for 100 nm Ch St sample. This shoulder
indicates additional UV absorption in this range. This can be due
to the nitrogen defects since all samples contain up to 2.5 wt % of
nitrogen.
[0096] Due to the rapid increase in UV absorbance when particle
sizes are increased to 60 nm and above, these particles are
believed particularly well suited for UV protection products for
both UVA and UVB protection. This aspect is discussed further after
discussion of all experiments. Note that all samples at all
particle size demonstrate very high absorbance in a part 190-290 nm
of UVC region (100-290 nm).
[0097] FIG. 5 depicts transparency to UV radiation (rather than
absorbance), and the scale was compressed to more readily see the
dramatic change in UV absorption exhibited near the 400 nm range as
a function of particle size. As a result of this experiment, it can
be concluded that use of initial particle agglomerate sizes in the
range of 60 to 150 nm can be used to substantially increase the UV
attenuation without significant impact on visible transparency in
relatively low concentrations of ND particles. When the visual
presence of the particles is of secondary consideration, or used to
augment pigmentation, even larger size particle agglomerates can be
used to produce even greater UV absorption. It is noted that the
particle agglomerate sizes may increase to varying degrees in
formulating the product dispersion. This factor should be taken
into consideration when determining how to formulate a UV
protecting composition based upon the desired protection and
visibility of the resulting product when in use. At this scale, the
190 and 360 nm particle agglomerate performance is too high to be
readable on the graph, but is nonetheless shown for
completeness.
Example 3
[0098] Dried films of DND were prepared on quartz substrates and
their absorbance spectra were recorded. In this experiment, 0.8 ml
of 1 wt % suspension of polydispersed Ch St ND in water was spread
over the 4-cm.sup.2 outer wall of a quartz cell and the water was
slowly evaporated at room temperature. The resulting amount of DND
in the film was 2 mg/cm.sup.2. The film was grey and not
transparent visually. In another experiment, a water suspension of
0.5 wt. % water suspension of a 25 nm fraction of Ch I6 nanodiamond
was spread over a 3'' quartz wafer (from Silicon West) placed on a
hot plate at 120.degree. C. The resulting dry ND film was visually
transparent with a brownish hue. The resulting amount of DND in the
film was 1 mg/cm.sup.2. FIG. 6 illustrates the absorbance spectra
of the two dried films. The grey non-transparent film prepared from
DND suspension with relatively large aggregates using Ch St shows
absorption that changes slightly over the entire UV-VIS region of
the spectrum. Additional spectra for this film were taken after
3-hour sun exposure (afternoon, August in North Carolina). The two
spectra were identical.
[0099] Despite the fact that the film made from 25 nm aggregate
sizes of ND is very thin and transparent in the VIS region,
absorption in UVA and, especially UVB and at shorter wave lengths
is high (FIG. 6). Also, it can be noted from the figure that the
specific absorption shoulder over the 340-420 nm wavelength range
for the Ch I6 25 nm fraction (FIG. 6), that increases the UV
absorption in this range, is present. This can be possibly due to
the presence of nitrogen defects in the nanodiamond lattice. Thus
thin ND film can be applied by different means for UV protection
over different surfaces (wood, polymers, etc).
Example 4
[0100] In this experiment 40 mg of Ch I6 powder was added to 10 g
of Yellow exterior 100% acrylic flat house paint (DuraCraft.TM.
brand paint was used). This resulted in 0.4 wt. % of ND in the
un-dried paint. The ND powder was dispersed using magnetic stirring
for 1 hr at 300 rpm. There was no visual difference between the
initial paint and the paint with the ND addition. Then the initial
paint and paint with ND addition were dispersed as a single layer
using a foam brush over identical thin glass substrates resulting
in approximately the same weight of paint. Three samples for each
type were prepared. The samples were dried over a period of 2 days
at room temperature. Then UV-VIS absorption spectra of the two
types of samples were taken. FIG. 7 illustrates the typical
increase in absorbance for all samples with the addition of ND to
the paint as compared to the samples of the paint on glass without
the addition of ND.
[0101] It is evident from this example, that ND particles can be
introduced directly into the finished paint or other coating after
formulation. Additionally, it appears that the ND particles could
be introduced by way of direct introduction into the final product
of ND particles in dry form, or mixed with a pigment, solvent or
other additive during the manufacturing process or as a final step
after packaging the product (e.g., at point of sale or use as a
constituent of a pigment or other additive).
Example 5
[0102] In this experiment 50 mg and 100 mg of Ch I6 powder was
added to 5 g of MinWax.TM. brand Fast-Drying Polyurethane Clear
Satin finish. This resulted in 1 wt. % and 2 wt. % of ND in the
un-dried finish composition. The ND powder was dispersed using
magnetic stirring for 1 hr at 300 rpm. Then the initial finish and
the finish with the addition of ND were dispersed as a single layer
using a foam brush over identical thin glass substrates resulting
in approximately the same weight of finish. Samples in duplicate
were prepared for both the finish with and without ND. The samples
were dried over a period of 1 day at room temperature. Then UV-VIS
absorption spectra for the samples with the two different ND
concentrations were taken. The UV-VIS absorption spectrum of a
sample of finish without the addition of ND was taken for
comparison. FIG. 8 illustrates the increase in absorbance that was
observed for all samples of Polyurethane Clear Satin finish after
the addition of 1 wt. % and 2 wt. % nanodiamonds.
[0103] Again, it is evident from this example, that ND particles
can be introduced directly into the finished polyurethane finish or
other coating after formulation. Additionally, it appears that the
ND particles could be introduced by way of direct introduction into
the final product of ND particles in dry form, or mixed with a
pigment, solvent or other additive during the manufacturing process
or as a final step after packaging the product (e.g., at point of
sale or point of use as a constituent of a pigment or other
additive).
Example 6
[0104] In these experiments water-based polyacrylic protective
finish Clear Satin (MinWax.TM. brand) was used. First, a water
suspension of 2 wt. % Ch Oz powder was prepared by sonication of
the suspension for a period of 10 min. Then 15 ml of the 2 wt. % ND
water suspension was added to 15 ml of the protective finish. The
suspension was stirred using magnetic stirring for 24 hrs at 300
rpm. For a control sample, 15 ml of pure water was added to 15 ml
of the finish and stirred. Then the initial finish with just water
added and the finish with ND suspension addition were dispersed as
a single layer using a foam brush over identical thin glass
substrates resulting in approximately the same weight of finish.
Samples in duplicate of each were prepared. The samples were dried
over a 1 day period at room temperature. The resulting ND content
in the dried film was 4 wt. %. Then UV-VIS absorption spectra for
the samples containing ND were taken and compared against the
UV-VIS absorption spectrum a sample with pure finish with the
addition of water without addition of ND. FIG. 9 illustrates the
increase in absorbance of Water-based Polyacrylic protective finish
after addition of ND suspension.
[0105] Again, it is evident from this example, that ND particles
can be introduced directly into the finished polyacrylic finish or
other coating after formulation. Additionally, it appears that the
ND particles could be introduced by way of direct introduction into
the final product of ND particles in dry form, or mixed with a
pigment, solvent or other additive during the manufacturing process
or as a final step after packaging the product (e.g., at point of
sale or point of use as a constituent of a pigment or other
additive).
Example 7
[0106] In these experiments Water-based Polyacrylic protective
finish Clear Satin (MinWax.TM.) with the addition of Ch Ox water
suspension described in the example 8 was applied over eastern red
cedar wood surfaces.
[0107] Before the finish application, all bare wood samples were
sanded with 150 grit paper then sanded with 220 grit paper in order
to produce a smooth finish. A first coat was applied as a single
layer using a foam brush over a wood substrate; in this case the
Clear Satin finish was thinned 50% with water to allow maximum
penetration. After the first layer was allowed to dry overnight, a
second layer of the finish with and without ND were applied to
different wood samples. Samples in duplicate were prepared. The
samples were dried over a period of 2 days at room temperature. The
resulting content of ND in the dried film was 4 wt. %. Since the
wood samples were not transparent, UV-VIS reflection spectra of the
finish surfaces were taken. FIG. 10 illustrates the relative
increase in the 45.degree. reflectance of wood coated with
polyacrylic finish containing 4 wt. % Ch Oz ND in the dried finish
as compared to the coating without ND. The increased reflectance in
the UV region of the water-based polyacrylic protective finish
after addition of ND reduces the penetration of the UV light
through the coating and can therefore be concluded to improve wood
protection from degradation due to UV radiation.
[0108] Again, it is evident from this example, that ND particles
can be introduced directly into the finished polyacrylic finish or
other coating after formulation. Additionally, it appears that the
ND particles could be introduced by way of direct introduction into
the final product of ND particles in dry form, or mixed with a
pigment, solvent or other additive during the manufacturing process
or as a final step after packaging the product (e.g., at point of
sale or point of use as a constituent of a pigment or other
additive).
Example 8
[0109] Several polyimid (PI) samples were fabricated with the
addition of nanodiamond particles at different concentrations of
Ch-St, Ch-Oz and Ch-Oz-B DND. ND powders were dispersed initially
in N-Methylpyrrolidone (NMP) solvent, then sonicated for 5 min and
mixed with commercial PI solution in NMP (PI-2611). PI-ND films
were distributed over 3'' diameter round glass substrates by the
spin-on technique at 700 rpm for 45 sec. The samples were pre-baked
in air for 120 sec at 120.degree. C. on a hot plate. Then the
samples were baked for 1 hr at 400.degree. C. in a N.sub.2
atmosphere. The sample thickness varied between 6-7 um over the
substrates. The most stable NMP organosols with high dispersivity
of ND particles were achieved using Ch-Oz, the ozone-treated
nanodiamond powder, and especially its smaller fraction Ch-Oz-B. As
small as 70 nm diamond particle sizes were achieved for NMP
suspensions with several wt. % of Ch-Oz-B as measured by photon
correlation spectroscopy (PCS) using a Beckman-Coulter N5 submicron
particle size analyzer. ND-polyimid films were fabricated for all 3
types of ND at concentrations of 1 wt. %, 2 wt. % and 3 wt. % of ND
in dried films.
[0110] Visually, the fabricated ND-PI nanocomposites were smooth
and rather transparent, even at 3 wt. % of ND, preserving the
yellowish color of pure PI samples. However, the transparency and
overall appearance of nanocomposite films baked on 3'' glass
substrates varies depending on the type of ND used in the
composite. These variations are believed to be due to different
scattering of light by the nanoparticles of different sizes. While
Ch-St samples with the largest particle size show some cloudiness,
films with Ch-Oz are of high quality in terms of transparency,
especially for the case of nanocomposite films prepared using the
smallest fraction of Ch-Oz-B. Ch-Oz samples have a high
concentration of oxygen-containing surface groups that probably
enhance their dispersivity in NMP solvent. Thus it is believed that
the type of surface groups on DND play a substantial role in
dispersion of DND in particular solvents and the related polymer
matrix. UV-VIS spectra indicate an increase in UV-VIS absorbance
for all films containing nanodiamonds as compared to the pure
polyimid film. The absorbance increased with increasing ND
concentration.
[0111] FIG. 11 illustrates the increase in absorbance for samples
containing 3 wt % of nanodiamonds for Ch St, Ch Oz and Ch Oz-B
ND.
Example 9
[0112] Nanodiamond films formed by drying ND suspensions on quartz
substrates as described in EXAMPLE 4 were used in this series of
experiments. The ND films confined between 2 quartz substrates were
visually transparent with a brownish hue. This ND coated quartz
structure was placed over several samples which otherwise lost
their color quickly under sun exposure (July in North Carolina). As
samples to demonstrate the protection from sun exposure provided by
ND films, we used pink Post-It.TM. page markers (3M (670-5AF)). The
page marker was covered in a way that part of it was covered by
quartz coated with a ND film, part was covered with only pure
quartz and part was open to air. After 2-days of sun exposure,
visually there was a boundary between the more bright pink color
preserved under the ND film and less colored part of the marker
that was not protected with ND film.
Example 10
[0113] In this example 30 mg of red water-color paint (dry) was
added to 2 ml of 0.2 wt. % of 40 nm average particle size of Ch I6
fraction suspended in DI water. Two milliliters of the paint was
added to 2 ml of pure DI water. The paint was dissolved in the
samples by shaking. Then two red lines were painted over white
cotton fabric. A portion of both lines (control) was protected from
the sun. The fabric was exposed to the sun for 2 weeks (July in
North Carolina). In 2 days the color of the portion of the lines
which was painted with only pure paint almost disappeared, while
the red-brownish color of the line with the addition of ND lasted
longer than 4 days. The water suspensions of the paint with and
without ND in glass vials were also exposed to the sun. After one
day the red color of the paint with no ND disappeared completely
and a white residue was seen in the vile, while the red brick color
of the paint water suspension containing ND was partially preserved
even after 2 weeks of sun exposure.
Example 11
[0114] In this example Crayola.TM. kids' paint (dense liquid state)
was used. The same amount of paint (pink, orange and green colors)
was placed to glass vials and 2 ml of pure water and 2 ml of 0.08
wt. % of 60 nm average particle size fraction of Ch I6 ND were
added. Samples were shaken and exposed to the sun for one week
(July in North Carolina). In the case of the bottles with orange
paint there was no visible change in the color of either the
control sample or the sample with ND addition. For the bottles with
pink and green paints there was visible bleaching of the color in
the control samples while the colors of the samples with ND
addition were much better preserved. The same paints were also
dispersed above glossy paper and left for a week outdoors. Better
color preservation was observed for samples with ND additions. In
addition, samples with ND additions adhered better to the paper
surface--after rain almost all paint without nanodiamond was
removed from the paper while samples with nanodiamonds still
covered approximately the original area.
[0115] From the above examples, it is evident that ND particles can
be introduced into a colorant or coating product directly into the
finished paint, varnish, polyurethane or other coating after
formulation. Additionally, it appears clear that the ND particles
could be introduced by way of direct introduction into the final
product of ND particles in dry form, or mixed with a pigment,
solvent or other additive during the manufacturing process or as a
final step after packaging the product (e.g., at the point of use
or at point of sale as a constituent of a pigment or other
additive). When formulating an additive or pigment for later
addition (e.g., addition of pigments during custom blending of
paints, stains or varnishes), the concentration of ND particles
should be adjusted to provide a suitable level of protection to the
final product. Moreover, some pigments are more susceptible to
deterioration in the presence of UV radiation. Hence, such pigments
may be formulated with higher concentrations of nanodiamonds and/or
larger nanodiamond particles than other pigments that are less
susceptible to degradation from UV radiation. Generally, however,
for additives or pigment products, the concentration of the ND
particles might be higher than the proportions listed above in
order to obtain a suitable concentration of the ND particles in the
final product to provide the target level of UV protection.
Furthermore, the ND particles can be introduced into the final
product by virtue of initial dispersion into any suitable
constituent of the final product including, but not limited to, a
binder, a solvent, an additive, a pigment, a diluent, a filler,
etc.
TABLE-US-00001 TABLE 1 FTIR analysis of the surface composition of
the ND used in the present study. Ch Oz (same Ch Chemical Oz- group
Ch St Ch I6 Black) Kr-b O--H free, 3573 cm.sup.-1 Shoulder 3590
3596 sh 3588 sh O--H, H weak cm.sup.-1 bridge (OH) --NH.sub.2,
.dbd.NH, 3432 cm.sup.-1 3432 cm.sup.-1 3423 3410 >NH broad broad
Above and - - - -- -- -- 3245 sh --CONH-- --CONH.sub.2-- Methyl
asym 2960 cm.sup.-1 -- 2960.1 -- very weak Methylene 2930 cm.sup.-1
-- 2931 2927.9 asym weak Methylene 2858 cm.sup.-1 -- 2859.5 2851.9
sym very weak ##STR00001## -- 1799 cm.sup.-1 as well at 1289
cm.sup.-1 1813.1 1773.9 ##STR00002## 1725 cm.sup.-1 -- -- --
--NH.sub.2, 1631.6 cm.sup.-1 1631.6 cm.sup.-1 1628.0 1627.3
>C.dbd.C< R--C(.dbd.O)O-- -- -- -- -- H1a diamond -- Very
weak -- -- feature, N-- shoulder 1460 related cm.sup.-1
(possibility) CH in CH.sub.3, -- -- 1446.1 1448.4 CH.sub.2
--CH.sub.3, -- -- 1370.1 -- >C(CH.sub.3).sub.2 >N--NO.sub.2
-- -- 1275.2 1319.6 sh C--N.dbd.O -- -- 1225.9 1210.5 C--OH, 1120.2
cm.sup.-1 -- 1060.1 -- adsorbed CO, medium CO.sub.2
>C.dbd.C(H)-- 802 cm.sup.-1 -- -- 920.74 extremely weak 3
neighboring 781 cm.sup.-1 -- -- -- aromatic C--H extremely weak
C--H 620 cm.sup.-1 -- 593.6 593.6 weak
[0116] Thus, a surface coating, colorant, pigment or polymer
composite consistent with certain embodiments that provides
resistance to degradation when exposed to at least some portion of
ultraviolet radiation having wavelengths between approximately 190
and 400 nm is made up of a dispersion of an effective amount of
diamond nanoparticles in a binding matrix, wherein at least a
portion of the diamond nanoparticles have a size greater than about
60 nm so that the diamond particles provide ultraviolet radiation
degradation resistance properties in the dispersion.
[0117] In certain embodiments, the surface coating or colorant has
a pigment that renders coloration to the surface coating or
colorant. In certain embodiments, the surface coating or colorant
has a solvent that is compatible with the binder. In certain
embodiments, the surface coating or colorant has at least a portion
of the diamond nanoparticles having a size of approximately 60-150
nm. In certain embodiments, at least a portion of the diamond
nanoparticles have a size of approximately 100 nm. In certain
embodiments, the diamond nanoparticles comprise up to 25.0 percent
by weight of the surface coating or colorant. In certain
embodiments, the nanoparticles comprise between about 0.5 and 5.0
percent by weight of the preparation. In certain embodiments, the
nanodiamond particles have a visible color or are luminescent, and
wherein the diamond nanoparticles impart a color to or modify a
color of the dispersion. In certain embodiments, the surface
coating or colorant is formulated as a paint, varnish, lacquer,
enamel, polycarbonate and polycarbonate blends, polyester,
polyester fibers, polybutylene terephthalate (PBT), acrylics,
polyamide, polyamide fibers, polyacetal, polyesters, unsaturated
polyesters, polyurethane, styrenics and other plastics and
coatings. In certain embodiments, the diamond nanoparticles are
modified as a result of wet or gas phase chemical reaction(s), or
chemical reactions induced photochemically, electrochemically,
mechanochemically, annealing, or by means of a plasma, irradiation
or sonic energy to obtain diamond nanoparticles with an enhanced
ability to absorb ultraviolet radiation. In certain embodiments,
the binding matrix is selected from the group consisting of: a
polymer matrix, an epoxy, polytetrafluoroethelyne, resins,
polycarbonates and polycarbonate blends, polystyrene,
polyurethanes, polyimides, acrylics, epoxies, methacrylic,
phenolics, silicones, polyesters, polyester fibers, unsaturated
polyesters, polyurethane foam (PUF), polybutylene terephthalate
(PBT), polyamides, polyamide fibers, polyacetals, vinyl polymers,
phenol formaldehyde, neoprene, rubber, silicone rubber compounds,
polypyrroles, polyaniline, polyacetylenes, polythiophenes,
poly-p-phenylenes, polyacrylthiophenes,
poly-p-phenylene-benzo-biz-thiozole (PBT), polymethylmethacrylate,
butadieneacrylonitrile, fibers, ceramics, glasses, polyethyelene
compounds with polyisobutylene, ethylene ethyl acrylate copolymers,
extruded polystyrene foam, and expanded polyvinylchloride and other
plastics and coatings. In certain embodiments, the binding matrix
containing the UV radiation attenuating nanodiamond particles is
suitable for application as a coating to a substrate using at least
one of an aerosol spray process, an electrostatic spray process, a
hot melt spray process, a high velocity high temperature spray
process, a thermal spray process, an ultrasonic spray process, a
fluidized bed process, a dipping process, a brushing process, a
spin-on process, a wipe-on process, a plasma spraying process, a
casting process, a molding process and an injection molding
process. In certain embodiments, an article is coated by the
surface coating or colorant.
[0118] In another embodiment, a paint or surface coating
preparation provides resistance to degradation when exposed to at
least some portion of ultraviolet radiation having wavelengths
between approximately 190 and 400 nm and includes a paint or
surface coating preparation including a pigment, a binder, and a
solvent that is compatible with the pigment and the binder; a
dispersion of an effective amount of diamond nanoparticles in a
paint or surface coating preparation; and wherein at least a
portion of the diamond nanoparticles have a size greater than about
60 nm so that the diamond particles provide ultraviolet radiation
degradation resistance properties in the dispersion.
[0119] In certain embodiments, at least a portion of the diamond
nanoparticles have a size of approximately 60-150 nm. In certain
embodiments, at least a portion of the diamond nanoparticles have a
size of approximately 100 nm. In certain embodiments, the diamond
nanoparticles comprise up to 25.0 percent by weight of the surface
coating or colorant. In certain embodiments, the nanodiamond
particles have a visible color, and wherein the diamond
nanoparticles impart a color to or modify a color of the
dispersion. In certain embodiments, the diamond nanoparticles are
modified as a result of wet or gas phase chemical reaction(s), or
chemical reactions induced photochemically, electrochemically,
mechanochemically, annealing, or by means of a plasma, irradiation
or sonic energy or modified during a process of nanodiamond
synthesis by introducing dopants and defects to obtain diamond
nanoparticles with an enhanced ability to absorb ultraviolet
radiation. In certain embodiments, an article is coated by the
paint or surface coating preparation.
[0120] In another embodiment, an ultraviolet radiation resistant
structure provides resistance to degradation when exposed to at
least some portion of ultraviolet radiation having wavelengths
between approximately 190 and 400 nm and has a substrate with a
layer of ultraviolet degradation resistant coating covering at
least a portion of the substrate, wherein the ultraviolet radiation
degradation resistant coating that includes an effective amount of
diamond nanoparticles dispersed in a binder, wherein at least a
portion of the diamond nanoparticles have a size greater than about
60 nm so that the diamond particles provide ultraviolet radiation
degradation resistance properties in the dispersion.
[0121] In certain embodiments, a pigment renders coloration to the
surface coating or colorant. In certain embodiments, a solvent that
is compatible with the binder is used. In certain embodiments, at
least a portion of the diamond nanoparticles have a size of
approximately 60-150 nm. In certain embodiments, at least a portion
of the diamond nanoparticles have a size of approximately 100 nm.
In certain embodiments, the diamond nanoparticles comprise up to
25.0 percent by weight of the surface coating or colorant. In
certain embodiments, the diamond nanoparticles comprise between
about 0.5 and 5.0 percent by weight of the preparation. In certain
embodiments, the nanodiamond particles have a visible color, and
wherein the diamond nanoparticles impart a color to or modify a
color of the dispersion. In certain embodiments, the diamond
nanoparticles are modified as a result of wet or gas phase chemical
reaction(s), or chemical reactions induced photochemically,
electrochemically, mechanochemically, annealing, or by means of a
plasma, irradiation or sonic energy or modified during the process
of nanodiamond synthesis by introducing dopants and defects to
obtain diamond nanoparticles with an enhanced ability to absorb
ultraviolet radiation.
[0122] A pigment or additive to a surface coating or colorant
preparation that provides resistance to degradation when exposed to
at least some portion of ultraviolet radiation having wavelengths
between approximately 190 and 400 nm, in accordance with certain
embodiments has a dispersion of an effective amount of diamond
nanoparticles in the pigment or additive, wherein at least a
portion of the diamond nanoparticles have a size greater than about
60 nm so that the diamond particles provide ultraviolet radiation
degradation resistance properties to the surface coating or
colorant preparation when dispersed therein.
[0123] In certain embodiments, the pigment or additive has a
solvent that is compatible with the pigment and the surface coating
or colorant. In certain embodiments, at least a portion of the
diamond nanoparticles have a size of approximately 60-150 nm. In
certain embodiments, at least a portion of the diamond
nanoparticles have a size of approximately 100 nm. In certain
embodiments, the diamond nanoparticles comprise at least 0.1
percent by weight of the pigment. In certain embodiments, the
nanodiamond particles have a visible color, and wherein the diamond
nanoparticles impart a color to or modify a color of the pigment or
additive dispersion. In certain embodiments, the diamond
nanoparticles are modified as a result of wet or gas phase chemical
reaction(s), or chemical reactions induced photochemically,
electrochemically, mechanochemically, annealing, or by means of a
plasma, irradiation or sonic energy or modified during the process
of nanodiamond synthesis by introducing dopants and defects to
obtain diamond nanoparticles with an enhanced ability to absorb
ultraviolet radiation. A surface coating or colorant may contain
the pigment or additive as a constituent thereof.
[0124] In accordance with certain embodiments, a method of
imparting resistance to degradation due to exposure to ultraviolet
radiation to a surface coating or colorant preparation when exposed
to at least some portion of ultraviolet radiation having
wavelengths between approximately 190 and 400 nm involves:
providing an effective amount of diamond nanoparticles, wherein at
least a portion of the diamond nanoparticles have a size greater
than about 60 nm; providing a surface coating or colorant
preparation; dispersing the nanodiamond particles into the surface
coating or colorant preparation, so that the diamond particles
provide ultraviolet radiation degradation resistance properties to
the surface coating or colorant preparation when dispersed
therein.
[0125] In certain embodiments, at least a portion of the diamond
nanoparticles have a size of approximately 60-150 nm. In certain
embodiments, at least a portion of the diamond nanoparticles have a
size of approximately 100 nm. In certain embodiments, the diamond
nanoparticles comprise at least 0.1 percent by weight of the
surface coating or colorant. In certain embodiments, the
nanodiamond particles have a visible color, and wherein the diamond
nanoparticles impart a color to or modify a color of the surface
coating or colorant. In certain embodiments, the diamond
nanoparticles are modified as a result of wet or gas phase chemical
reaction(s), or chemical reactions induced photochemically,
electrochemically, mechanochemically, annealing or by means of a
plasma, irradiation or sonic energy or modified during the process
of nanodiamond synthesis by introducing dopants and defects to
obtain diamond nanoparticles with an enhanced ability to absorb
ultraviolet radiation.
[0126] A polymer composite material, consistent with certain
embodiments, exhibiting resistance to degradation by exposure to at
least some portion of ultraviolet radiation having wavelengths
between approximately 190 and 400 nm has a dispersion of an
effective amount of diamond nanoparticles in the polymer composite,
wherein at least a portion of the diamond nanoparticles have a size
greater than about 60 nm so that the diamond particles provide
ultraviolet radiation degradation resistance properties to the
polymer composite. In certain embodiments, the composite has a
solvent that is compatible with the polymer composite. In certain
embodiments, at least a portion of the diamond nanoparticles have a
size of approximately 60-150 nm. In certain embodiments, at least a
portion of the diamond nanoparticles have a size of approximately
100 nm. In certain embodiments, the diamond nanoparticles comprise
at least 0.1 percent by weight of the polymer composite. In certain
embodiments, the nanodiamond particles have a visible color, and
wherein the diamond nanoparticles impart a color to or modify a
color of the polymer composite. In certain embodiments, the diamond
nanoparticles are modified as a result of wet or gas phase chemical
reaction(s), or chemical reactions induced photochemically,
electrochemically, mechanochemically, annealing or by means of a
plasma, irradiation or sonic energy or modified during the process
of nanodiamond synthesis by introducing dopants and defects to
obtain diamond nanoparticles with an enhanced ability to absorb
ultraviolet radiation. In certain embodiments, the composite is
cured to a solid state. In certain embodiments, the polymer
composite is applied to a UV transparent free standing support
structure. In certain embodiments, the free standing support
structure is glass. In certain embodiments, the polymer composite
is sandwiched between two sheets of glass.
[0127] While certain illustrative embodiments have been described,
it is evident that many alternatives, modifications, permutations
and variations will become apparent to those skilled in the art in
light of the foregoing description.
* * * * *